First Build Log - OM 6-String

[Eric Knapp]

Well, I went out and checked the entire board carefully and there are lots of cracks. I tried to find some sections with no cracks that were long enough and got 2 more. I have one from the first try too so I have 3 halves of tops. Heh.

The sections I got with no cracks are not contiguous so they don't match quite as well.

New Top Rough Cut Side

If this one doesn't develop any cracks I'll use it. I surfaced one side before I resawed them.

New Top Surfaced Side

I'm going out of town next weekend so I won't have a good block of time for a couple of weeks. I hope there won't be any cracks the next time I am able to put some time in. This top won't be as pretty maybe but there has to be a first guitar I follow through with and finish.

From a 13' board I may get one guitar. I suspect this is not a new experience.

-Eric

[Eric Knapp]

I am looking at my cedar and was wonder what it would look like as a guitar. I think most of you can do this in your mind's eye now. I needed some help.

Mockup

This might have some potential.

-Eric

[Barry Daniels]

It would look more balanced if you removed the sap wood off that one side.

[Eric Knapp]

It would look more balanced if you removed the sap wood off that one side.

Good tip. That pic was before I jointed them and I took off a fare amount. I'm not sure how much sap is left. I'll post a new pic once I thickness it.

-Eric

[Eric Knapp]

I had a moment this weekend to be in the shop. I started working on a plexiglass template from the OM planes I have.

Plexi Template

I'm being careful to get this right. It seems like lots of things will come from this initial shape. Here's the almost ready template on the glued top. No cracks have formed on the top so I'm encouraged.

Template on Top Blank

My instinct is to build the mold next. There are molds for an OM-style guitar available but I want the experience of making my own. I also want to use the money for other things instead of a mold. I hope this isn't just being penny wise.

-Eric

[Bryan Bear]

IMHO you should absolutely make the mold next. I make an outside template of half the shape that I use to rout out all the pieces to stack and laminate for the mold halves. If you cut them out carefully on the bandsaw you can use the middle sections to laminate a bending form slightly undersized to account for the thickness of the sides. You won't need this if you are just bending on the pipe. . . That outside template is nice to have for placing on boards to see how the outline fits the features of a board you are considering resawing.

Get the shape of your plexiglass template right but don't expect to use it to make each part. Don't, for example, cut out the top and back profile with it before you make the rim. There's a dirty little secret that nobody talks about with instrument making. It is an analogue process (for some more-so than others). With every step in the process you will move a little bit away from the outline on your drawing. Especially on the first few instruments, it is best to rough trim your plates with using the shape of the rim rather than the template.

Don't be alarmed if you rim shape ends up pretty far away from the shape of the drawing. You are the only one who will notice. You would be surprised at how much asymmetry you could get away with. As long as you can establish a center line and it fits in the case you're in good shape. If you do notice the rim is a bit out of whack in length, it might be a good idea to place your braces based on measurements from the 14th fret and outside of the rim at the heel. You'll be placing your bridge based on the fretboard, if you place your braces and birdgeplate based from the tail or waist you could be off.

[Eric Knapp]

IMHO you should absolutely make the mold next. I make an outside template of half the shape that I use to rout out all the pieces to stack and laminate for the mold halves. If you cut them out carefully on the bandsaw you can use the middle sections to laminate a bending form slightly undersized to account for the thickness of the sides. You won't need this if you are just bending on the pipe. . . That outside template is nice to have for placing on boards to see how the outline fits the features of a board you are considering resawing.

I am bending on a pipe, that's all I have and will probably be the only have thing I have for a long time.

Get the shape of your plexiglass template right but don't expect to use it to make each part. Don't, for example, cut out the top and back profile with it before you make the rim. There's a dirty little secret that nobody talks about with instrument making. It is an analogue process (for some more-so than others). With every step in the process you will move a little bit away from the outline on your drawing. Especially on the first few instruments, it is best to rough trim your plates with using the shape of the rim rather than the template.

That's a great tip. I have done enough wood working that I fully expect the final size to drift from the plans. Starting from a known shape is a good thing but it's wood.

Don't be alarmed if you rim shape ends up pretty far away from the shape of the drawing. You are the only one who will notice. You would be surprised at how much asymmetry you could get away with. As long as you can establish a center line and it fits in the case you're in good shape. If you do notice the rim is a bit out of whack in length, it might be a good idea to place your braces based on measurements from the 14th fret and outside of the rim at the heel. You'll be placing your bridge based on the fretboard, if you place your braces and birdgeplate based from the tail or waist you could be off.

I would never have thought about the correct reference point. This is gold!

Thanks, Bryan.

-Eric

[Eric Knapp]

I stole some shop time this evening. My plexi template is getting closer. I think it's the right shape and I'm starting to mark the locations of the braces and sound hole.

Plexi Template and Spruce

The hunk of wood is quarter-sawn Sitka that will be the braces.

-Eric

[Eric Knapp]

Well, I have no idea what I'm doing but if I keep trying to get ready I'll never do it. I thinned the cedar top to a good starting point today. I used my general woodworking instincts and my experience with handplanes to do this. I made a carriage for the top out of MDF. It is two layers of 3/4" glued together. The hardboard around the edges is just a bit thicker than the final top dimension.

Thicknessing Carriage

The top fits in it very tightly.

Top in the Carriage

I sharpened the iron in my big ECE 24" joiner plane and thinned it to the top of the hardboards. The joiner did a great job of getting right to the hardboard everywhere.

After Joiner Plane

Then I switched to my freshly sharpened ECE Primus Smoother and started leveling and thinning. That's a great plane.

Smoother for Final Passes

Measuring and planing in a loop is next.

-Eric

[Eric Knapp]

I smoothed and leveled both sides and measured. I got it to 3.5mm very consistently. My goal thickness is 3.2 so this seemed like a good start. I've thinned and surfaced thicker boards and the carriage was my idea to make the thin panel more like the thicker ones I'm used to.

3.5mm

After a few more iterations of smoothing and measuring I got it to 3.2mm.

3.2mm

The top is now pretty even at 3.2mm with one area that got to 3.1. Doing it all my hand for the first time on a top and getting that close seems OK to me.

3.1mm

Both sides of the top are smooth and level and I think I'm ready for the next step. And, wow, softwoods sure are fragile when they get that thin. It seems like a thinned top has to be treated very carefully to not damage it. Is it just that this is cedar? Is spruce that fragile?

Progress is being made and learning is happening. That's making me happy. Let the mistakes come, I'm ready for them.

-Eric

[Barry Daniels]

Looks good to me. Yeah, they are pretty fragile when that thin and are prone to cracking along the grain if flexed too far. They also dent easily so be careful where you lay it or what you place upon it.

[Eric Knapp]

Looks good to me. Yeah, they are pretty fragile when that thin and are prone to cracking along the grain if flexed too far. They also dent easily so be careful where you lay it or what you place upon it.

Thanks, Barry. I've noticed the denting already. The cedar can be dented with fingers even. Now that I have a thinned top I am looking towards the next step. It seems that there are several steps that can be done independently. I have to make/buy a rosette, tool up to install the rosette, make a mold, and select the wood for the back and sides for starters. Quite a list.

-Eric

[Barry Daniels]

Tooling for cutting a rosette channel can be as simple as a popsicle stick with a nail protruding at one end and an X-acto knife blade barely protruding from the other end with the appropriate distance between them. Or you can use a dremel in a base with a homemade radius setup.

[Beate Ritzert]

I've noticed the denting already. The cedar can be dented with fingers even.

But You can "undent" it by putting a tiny drop of water on the dented spot (with a needle...)

[Eric Knapp]

I've noticed the denting already. The cedar can be dented with fingers even.

But You can "undent" it by putting a tiny drop of water on the dented spot (with a needle...)

Thanks for the tip. Do you sometimes need to boil the drop of water with a soldering iron?

-Eric

[Barry Daniels]

Yes, it is the steam that expands the dented wood. I use the tip of a household iron. And I do not place the water directly on the wood. I place a clean cotton cloth over the wood, apply a few drops of water and touch it with the hot iron. This works immediately.

[Eric Knapp]

I got a brand new 1/8" spiral downcut bit for my laminate trimmer. It seems like a solid tool and I thank Todd for the recommendation.

Circle Jig and Channel

With it I was able to make my first trial rosette channel.

First Channel Trial

This is cedar and I've gathered from you all that this is a challenge to get a good edge. This seems acceptable for my first serious effort in a scrap.

First Trial Channel Closeup

How does it look?

-Eric

[Eric Knapp]

I didn't want to wait for dyed veneer or fiber and I happened to have some ebony strips. I cut some 1/16" by 1/16" strips on my bandsaw and scraped them smooth on 3 sides. I got out my bending iron which I have not used much yet. I'm total rookie for bending and I just decided to try to bend these tiny strips of ebony. Why not, eh?

After it finally warmed up I was able to do this.

Ebony Edging

That was a fun experiment and I actually bent it too much and had to figure out how to relax the bend to fit.

It seems to fit well.

Edging Closeup

With very little pressure it seals the joint.

Here's another closeup just because I like it.

Another Gratuitous Closeup

And it wouldn't be a rookie bending session without this.

Bending Ebony is Fun

As you all know, and I'm finding out, it takes a delicate touch to bend small piece of thin wood. This is a skill I hope to improve on very soon with the sides of this guitar.

I feel like I'm making progress, but anything feels like progress to me if I'm in the shop.

-Eric

[Barry Daniels]

The rosette channel looks good. The ebony strips, not so much.

If you make strips that are a maximum of .032" thick then you won't have to pre-bend them. They will be flexible enough to bend cold. Better yet, just buy them. They are relatively cheap and they will be very smooth so you will have a better fit against the rosette channel side walls.

Another approach is to buy standard veneer sheets. You can get dyed veneer in various colors (including black) and two thicknesses from LMII. I have also bought lots of high quality veneer in many species from eBay. Use a sharp utility knife and a steel ruler to cut off strips about an 1/8" wide. Stand them on their side and they become purling.

[Eric Knapp]

The rosette channel looks good. The ebony strips, not so much.

I am trying to learn and I'm curious what you think is not good about them. They are rough on top but stick up high enough so that doesn't matter. What could I do to make them better? They are sitting in the channel with no pressure on them to fit against the side wall of the channel. If I press just a little they fit perfectly with no visible gaps using a magnifier.

If you make strips that are a maximum of .032" thick then you won't have to pre-bend them. They will be flexible enough to bend cold. Better yet, just buy them. They are relatively cheap and they will be very smooth so you will have a better fit against the rosette channel side walls.

I wanted to try something without having to buy and wait for a shipment. I'm trying to use as much on-hand materials as I can, but I also want to do a good job. This was a trial to see what it was like and to start bending something.

Another approach is to buy standard veneer sheets. You can get dyed veneer in various colors (including black) and two thicknesses from LMII. I have also bought lots of high quality veneer in many species from eBay. Use a sharp utility knife and a steel ruler to cut off strips about an 1/8" wide. Stand them on their side and they become purling.

I have some maple and cherry veneer but nothing really black. I will see if there's anything local. I will also try a different approach to making ebony veneer. I have a fair amount of ebony chunks that are too small for most guitar parts but are long enough for this.

Thanks for the feedback, it's always helpful and educational.

-Eric